TY - CHAP M1 - Book, Section TI - Human Leukocyte and Platelet Antigens A1 - Franz, Brian J. A1 - Land, Geoffrey A. A1 - Vassallo, Ralph R. A2 - Kaushansky, Kenneth A2 - Prchal, Josef T. A2 - Burns, Linda J. A2 - Lichtman, Marshall A. A2 - Levi, Marcel A2 - Linch, David C. PY - 2021 T2 - Williams Hematology, 10e AB - SUMMARYThe gene products of the major histocompatibility complex (MHC) in humans are designated human leukocyte antigens (HLAs) since they were first described as cell surface antigens of blood leukocytes. The HLA antigens are highly polymorphic glycoproteins encoded on the short arm of chromosome 6. There are three classes encoded in the HLA region: class I (A, B, and C loci), class II (DR, DQ, and DP loci), and class III (tumor necrosis factor, complement factor genes, etc). The biological function of class I and II antigens is to act as the gatekeepers to the human immune response by presenting antigenic peptides to T lymphocytes. Class I antigens are present on almost all nucleated cells, whereas class II antigens are primarily expressed on B cells (along with class I determinants) and other antigen-presenting cells such as dendritic cells, endothelial cells, and monocytes. These antigens and their associated antibodies play key roles in hematopoietic cell and solid organ transplantation compatibility. They are also intimately involved in allosensitization to nonleukoreduced blood components, leading to platelet transfusion refractoriness. Other clinically important lineage-specific white cell antigens include those on neutrophils, which are much less polymorphic and less commonly a cause of clinical problems than the MHC system. Antibodies to neutrophil antigens play a role in alloimmune neonatal neutropenia, autoimmune neutropenia, and transfusion reactions such as transfusion-related acute lung injury. Platelets also possess a relatively limited number of platelet-specific polymorphic antigens that are involved in clinical disease states such as fetal/neonatal alloimmune thrombocytopenia, posttransfusion purpura, platelet transfusion refractoriness, and other alloimmune thrombocytopenias. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - hemonc.mhmedical.com/content.aspx?aid=1180471270 ER -